The long term objective of this proposal is to devise a very rapid inexpensive mutagenesis test which could be used to screen chemical compounds in industry, the environment, and food. The correlation between mutagenicity and carcinogenicity would identify these compounds as potential carcinogens/teratogens. The specific aim is to devise a system using molecular genetics, which gives a very rapid, sensitive and easily assayed response to low concentrations of mutagens. A mutagen screening test which has the same reliability as the Ames test, but is inexpensive, extremely rapid, capable of automation and consequently could be used to screen hundreds of compounds per day would have an extremely competitive commercial application.